Black cat walking

Feline hypertrophic cardiomyopathy

Feline hypertrophic cardiomyopathy is the most common heart condition in cats.

Hypertrophic cardiomyopathy (HCM) is a heart condition which causes the walls of the heart to thicken. This means your cat's heart has to work harder to pump blood around their body. It can also lead to complications such as blood clots forming.

Although HCM is a serious condition, cats can often live for years before the condition is diagnosed. Early diagnosis and treatment can help manage symptoms and improve your pet's quality of life. However, problems due to HCM can start very suddenly and be very serious, so it’s important to know the signs so you can get help as quickly as possible.

What are the symptoms of feline hypertrophic cardiomyopathy?

Many cats with feline hypertrophic cardiomyopathy will not appear to be ill so it's important to get them checked regularly and be aware of the increased risk to some cats. 

In some cases, your cat may suddenly develop serious signs as HCM can cause heart failure or a blood clot. Symptoms include:

  • laboured, rapid or open-mouthed breathing
  • lethargy (being more tired than usual)
  • difficulty eating or eating less
  • fainting
  • pain in their hind legs or paralysis (inability to move their legs)

Sadly, in some cases, sudden death will be the first sign that your cat has anything wrong with their heart. This will be a big shock. Remember that it's not your fault. Some illnesses are hard to detect and, even with treatment, may not have prevented their death. To speak to someone about your loss, details of our Pet Loss Support service are towards the bottom of this page.


Contact your vet as soon as possible if your cat shows any of these signs.

What causes feline hypertrophic cardiomyopathy?

The causes of HCM aren’t yet fully understood and, sadly, in many cases the causes of the condition are unknown. However, there are some factors that might increase your cat’s risk of developing HCM, including their genetics.

Genetic causes of hypertrophic cardiomyopathy

Some breeds of cat are more likely to develop hypertrophic cardiomyopathy, including:

  • Maine coon
  • ragdoll
  • British shorthair
  • sphynx
  • Persian

If you have one of the breeds listed above, speak to your vet about hypertrophic cardiomyopathy and any other health risks. 


Remember that any breed can develop HCM, so you should still get your cat checked by a vet regularly.

How is feline hypertrophic cardiomyopathy diagnosed?

You vet will usually carry out some routine tests such as a physical examination and listening to your cat's heart. 

If they find signs of HCM such as a heart murmur or abnormal heart rhythm then they may have some more tests such as:

  • an echocardiogram which uses ultrasound to show an image of your cat's heart. If your cat has HCM, the images will show thicker walls of their heart than a healthy pet.
  • a chest X-ray
  • an electrocardiogram (an ECG) which looks at the heart's rhythm
  • a blood test

If you’re thinking of breeding from your cat and they are a breed that has higher risk of developing HCM then your vet may recommend genetic screening tests to look for gene mutations that can be linked to HCM.

How is feline hypertrophic cardiomyopathy treated?

Although feline HCM is a serious condition, cats can often live with it for many years. If they have no symptoms or complications, your vet may recommend regular check-ups and talk you through more serious signs to look out for.

However, the condition is progressive and will often get worse as your pet gets older. If this happens your vet will talk you through managing the condition - sadly, there is no cure. 

Treatments for managing feline HCM include medication to help maintain your cat's quality of life for as long as possible and prevent any complications, like blood clots.

Life expectancy for cats with HCM

Unfortunately, as each cat is so different and will be diagnosed at a different time, it's hard to predict how long they'll live after being diagnosed. Your vet will talk through treatment options for your cat which can help them have a good quality of life for months or even years.

If you are concerned about your cat's quality of life and their health, speak to your vet. You and your family know your cat better than anyone else, but you may find it helpful to read about when it's the right time to say goodbye. Or you can speak to our pet loss team.

Pet Loss Support offers support to grieving pet owners, through a national network of trained volunteers. We're here seven days a week via phone, email and webchat.

We also have a Facebook group if you'd like to join a community of people supporting each other through their grief.

— Page last updated 20/12/2023